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Alcoa of Australia Residue Management
Residue Reuse
Alcoa of Australia generates a significant amount of residue which is stored in residue drying areas on Alcoa owned property. As a leader in sustainability, Alcoa is committed to ensuring sustainability principles are applied to the management of bauxite residue.
Development of alternative uses for bauxite residue, with the aim of reducing the size of our residue areas, continues to be one of the major objectives for our residue research program. This program is run by our refining research and development team, known as the Technology Delivery Group (TDG). TDG is based at Kwinana Refinery in Western Australia and leads the development of residue reuse opportunities for Alcoa globally.
Our leadership in relation to residue sustainability is demonstrated in the development of a full scale ‘Carbon Capture’ plant in operation at Kwinana. Scroll down for more.
Reuse of residue sand is already happening within our operations and is another demonstration of residue being put to a sustainable use. The residue sand is used in the construction of residue drying areas and in surface capping for residue rehabilitation. If we didn’t have this sand we would have to import it, and with the sand shortage in WA our reuse is a real benefit to Alcoa and the community.
Alcoa of Australia is also focused on developing and commercialising strategies to reuse our residue externally with real opportunities coming from this work. Alcoa’s efforts in residue reuse research are far ahead of any of our competitors and we are certainly leading the industry in terms of promoting this as a key sustainability issue for our industry. We believe bauxite residue has the potential to become a valuable by-product in the future.
Alcoa of Australia has examined a range of potential uses for the sand and mud components of bauxite residue, including:
- As a soil amendment for broad use acre farming and horticultural uses;
- As a sand for use in cement manufacture;
- In effluent treatment ponds and septic systems;
- For trace metal retention from road runoff, rubbish tips and acid mine drainage;
- In ceramic manufacturing;
- In plastics manufacturing; and
- For use as a road base.
The three most promising potential products to be developed from bauxite residue are: red sand; Red LimeTM and Alkaloam®.
Red sand is essentially crushed rock and initial testing shows it could be used as a general fill material, a construction backfill or as a material suitable for road base construction.
Red limeTM is a by-product removed during the refining process that is then washed and dried. Red LimeTM has a high acid neutralising value and therefore has applications in pH control in agriculture or industrial systems. Red LimeTM could be more effective than most available pH control products because of the fine particle size and sodium carbonate that remains with the product. Work is currently underway to evaluate the feasibility of producing a Red LimeTM by-product, with the initial focus on use as an agricultural lime.
Alkaloam® is the fine-grained residue often referred to as red mud. Testing shows there are real benefits of adding this material to sandy soils which are common in coastal regions of Western Australia. Alkaloam® has proved successful as a soil amendment for nutrient deficient, acid soils and can increase the productivity of farmland. It has shown to reduce the amount of excess nutrients getting into our waterways. Those excess nutrients can cause serious environmental problems. Alkaloam® prevents phosphorous from being washed away from farms into waterways – which ultimately can help prevent algal blooms and fish kills.
Alkaloam® is alkaline which increases the soil pH in the same way as agricultural lime. However, lime can take a number of years to effectively reduce the pH of soil – but Alkaloam® can achieve this almost straight away. This means that Alkaloam® allows farmers to gain maximum benefits from the adjustment in soil pH instead of waiting for a soil response over one or more rainy seasons.
Carbon Capture Technology
Alcoa currently has a full scale ‘Carbon Capture’ plant in operation at the Kwinana Refinery in Western Australia. This unique process mixes carbon dioxide (a greenhouse gas) with bauxite residue to reduce the alkalinity of the material, thus reducing residue drying time, and providing a sink for what is usually a waste gas released into the atmosphere. As well as reducing greenhouse gas emissions, other flow on benefits include:
- Decreased potential for groundwater impact;
- Decrease in the area required to dry mud;
- Decreased risk of dust lifting from carbonated residue; and
- Creation of more opportunities for residue reuse.
Kwinana’s ‘Carbon Capture’ plant has the capacity to lock up 70,000 tonnes of carbon dioxide each year.
Through our membership of the Kwinana Industries Council we continue to contribute to research into how Kwinana industries can achieve ‘waste’ synergies by using each others’ by-products - carbon capture is one of those ways. The plant locks up carbon dioxide from a nearby ammonia plant, demonstrating how industry can form sustainability partnerships to reuse waste products.
While we are working towards implementing this technology in all of our refineries, a carbon dioxide source is needed for the process to take place. At Kwinana the nearby ammonia plant is the carbon dioxide source, however there are no similar sources near our other WA refineries. Alcoa is working towards being able to use our own carbon dioxide in the carbon capture process and the technology needed to do that is in development.
For more information on Carbon Capture click here .
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